ADDITION CONJUGUEE DE DERIVES LITHIES DE DITHIANE-1,3 AUX ALDEHYDES αβ ETHYLENIQUES

Article abstract of DOI:10.1016/0040-4020(82)80108-7

In order to synthesize γ carbonyl aldehydes which are interesting precursors in organic synthesis, we examine the action of masked acylanions, the lithiated derivatives from 1,3-dithiane 1a and 2-phenyl-1,3-dithiane on selected unsaturated aldehydes: crotonaldehyde 2, cinnamaldehyde 3, 3-methyl butenal 4 and methacrolein 5.In THF 1a leads with the four aldehydes to allylic alcohols.However 1b gives products resulting from C=C and C=O additions.Using THF-HMPA, we show that C=C addition is generally enhanced.Furthermore, in all cases examined C=C and C=O addition take place under kinetic controll: the regioselectivity observed can be interpreted by repulsive interactions due to the substrate and the reagent structure as well as lithium-carbonyl compound interactions.